The invention relates to a method for exchanging data between a device for programming and triggering electronic detonators and the detonators, wherein a plurality electronic detonators are disposed one behind the other in an ignition circuit, an address is assigned to each of the electronic detonators, the detonators are triggered in a specifiable delay sequence and data are generated by a time sequence of signals having a specified voltage.
In the extraction of raw materials deposited in the earth, it is necessary to clear away rock masses preventing access to the raw materials and then to obtain the raw materials from their deposits by crushing. During this excavation method, explosions are carried out in which explosive charges disposed in many boreholes are detonated consecutively in accordance with a certain time schedule.
A method of controlling explosion detonators and a so-called coded structure for controlling the blasting are disclosed, for example, in EP 0 588 685 B1. The electronic detonators of the explosive charges form an ignition system. The electronic detonators are commonly connected to a programming and triggering device via a so-called bus line. Via said bus line, the electronic detonators are activated and receive electrical energy that is capacitively stored by them. If the capacitance of a detonator is charged, it is capable of independently remaining in operation with the aid of the energy stored in its capacitor. The stored energy safeguards the ignition function and also the communication function between the detonator and the programming and triggering device of the detonators.
As a rule, every individual detonator has an address that is assigned to it and comprises a multidigit digital code. The delay time that determines the instant at which the respective detonator is detonated is transmitted in the form of coded signals to every individual detonator. The signals may consist of a polarity change of a specified voltage having a specified amplitude. The delay time is coupled to an address code so that every detonator charges only for the delay time assigned to it on the basis of the address code. After the detonator has received the transmitted data assigned to it, it has to respond so that it is possible to confirm that the delay time has been received and stored correctly by the electronics of the detonator.
During the communication of a detonator with the programming and triggering device of the detonator, problems occur in that the other detonators connected to the bus line are capacitive resistances that affect the transmission of the data. The data signals comprise, as a rule, a polarity change in a certain time sequence and in a certain number. These polarity changes are distorted by the capacitive resistances so that a clear transmission of the signals is not always guaranteed. Taking into account the capacitive resistances, the data transmission rates per unit time are low and the programming of a detonator, which takes place in the dialogue of the electronics of the detonator with the programming and triggering device of the detonators, is time-consuming and not always fault-free.
The object of the present invention is therefore to make the exchange of data between an electronic detonator programming and triggering device and the detonators more reliable and more rapid.
According to the invention, prior to an intended communication of an electronic detonator with the detonator programming and triggering device, there is applied to the ignition circuit for a specified time a direct voltage that is greater than the voltage of the signals with which the data are generated that the detonator transmits as a response. The increased voltage is below a critical voltage for triggering a detonator. As a rule, the detonators are designed in such a way that they are resistant, i.e., are not triggered, to a voltage that is at a certain height above the nominal voltage provided for generating the signals for communicating with the detonators. According to the invention, the tolerance range provided is, however, not exhausted in order to avoid any risk. On the other hand, the amplitude of the voltage is chosen in such a way that the capacitances of the other detonators are charged within a very short time to such a level as to avoid an attenuation of the voltage with which the detonator response signals are generated.
To transmit the detonator response, the voltage is reduced and the signals of the data that the detonator transmits as a response are generated at a lower voltage. During the transmission of the signals of the responding detonator, all the other detonators are charged to such a high level that they are no longer capacitive resistances and communication is thereby possible at a very high data transmission rate per unit time. The voltage in the ignition circuit is increased during such a time a such a value that, during the subsequent detonator response, capacitances of the other detonators do not have to be charged as a result of charge losses.
The magnitude of the capacitive and ohmic resistances within the ignition circuit depends on the number of connected electronic detonators. In a further advantageous refinement of the invention, it is possible that the capacitive resistance is ascertained and the minimum direct voltage necessary to charge the capacitances is determined as a function of its magnitude. In addition, the voltage drop due to the ohmic resistances can be compensated for. The increase in the direct voltage can consequently be matched individually to the particular application case. In addition, this ensures that the voltage does not exceed a critical value that results in the triggering of a detonator.